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Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Mailbutler - Mailbutler adds lacking functionality to email clients and increases your productivity
Mailbird - Mailbird is the best email client for Windows 7, 8 and 10
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eM Client - eM Client is a fully-featured email client for Windows and macOS with a clean and easy-to-use interface. eM Client also offers features for calendars, tasks, contacts, notes, and chat.